. .. ..* -a 5:; "5 87 < ` . iS :3400 ( Part XXI ) - 1980 ( Rearmed 2003 1993 ) ) ( Reaffirmed Indian Standard METHODS OF TEST FOR VULCANIZED PART XXI GASES DETERMINATION - CONSTAN? RUBBERS TO OF PERMEABILITY PRESSURE METHOD ( Second Reprint MAY 1997 ) 1JDC I 678.43 : 620.193.29 BUREAU OF INDIAN STANDARDS MANAKBHAVAN, 9 BAHADURSHAHZAFARMARG NEW DE1 III IInnfl? Febrzu7ry 198 1 Gr 4 1s : 3400 ( Part XXI ) - 1986 ( Reallirr~led 1993 ) Indian Standard METHODS OF TEST FOR VULCANIZED RUBBERS PART XXI GASES Rubber DETERMINATION -CONSTANT Products Sectional OF PERMEABILITY PRESSURE METHOD Committee, PCDC 13 TO Chairman Escort SHRI A. T. BASAK Consultants Representing Pvt Ltd, of Calcutta Supplies & Disposals, Directorate General New Delhi Ministry of Defence Directorate General New Delhi I) Alkali & Chemical Calcutta (R & D ) of Technical DeveIopment, Corporation of India Ltd, Export Inspection Council of India, Calcutta SIII~J 1'. K. CIIATTFXJBIC ( Alternate ) Sfilrl S. B, GANCULI Dunlop India Ltd, Calcutta SIIRI P. N. S. hl~m (Alternate ) Srmr A. Grsmoa JOAN Madras Rubber Factory Ltd, Madras Sur11 I<. J. A~XAHAN ( Altertrnte ) SII IL, A. GRO~H National Test House, Calcutta Cosmos India Rubber Works Pvt Ltd, Bombay YHRI LAIJT Ivforrm JA~INA~AS SliRI PULIN L. kINAI:IWAId ( AkeTde ) Indian Oil Corporation Ltd ( Marketing Division ), Saxr R. C. JHIXGAN Bombay Sl!nr hf. K.J.\r:;( rlltemate ) 5x:1 s. v. LATUI.4 Lathia Rubber Manufacturing Co Pvt Ltd, Bombay SE!:1 Y. S. LATIIIA (&kWIUk) 1311. - S. __K. . RAY (&!/mole) ( Contirwed on page 2 ) BUREAU OF INDIAN STANDARDS This publication is protected under the Indian Copyright Act ( XIV of 1957 ) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an infringement of copyright under the said Act. IS : 3400 ( Part XXI ) - 1980 ( Continued from page 1 ) Members SHRI S. K. MAHESHWARI Representing Indian Petrochemicals Corporation Ltd, Vadodara SHRI R. S. PATEL (Alternate ) Dn S. P. MANX Ministry of Railways SHRI D. N. V. C~ELLA~~ ( Ahwwte) DR W. MILLNS Indian Rubber Manufacturers Research Association, Bombay Sundaram Industries Ltd. Madurai SHRI N. NAQARAJAN SHRI P. VIJAYARAC+~AVAN( Alternate ) SBRI S. C. NAX~Y Bata India Ltd, Calcutta SHRI S. SARKAR ( Alternate ) SHRI R. R. PANDIT Bayer ( India ) Ltd, Bombay SHRI D. J. BHARUCHA ( Alternate ) National Rubber Manufacturers Ltd, Calcutta SHRI K. S. RADRAKRISHNAN SHRI R. P. MATHUR ( Alternate ) SHRI N. M. REQE Synthetics and Chemicals Ltd, Bombay SRRI R. N. MEHROTRA ( Alternate ) SHRI B. B. SANGTANI All India Rubber Industries Association, Bombay SHRI V. N. MAKAR ( Alternate ) SHRI B. C. SEN Ministry of Defence ( DGI ) SHRI R. K. GUPTA ( Alternate ) SHRI E. V. THOMAS Rubber Research Institute of India, Kottayam DR M. G. KUMARAN ( Alter&e J SHRI M. S. SAXENA. ' Director General, IS1 ( Ex-o&o Member ) Director ( P & C ) Secretary SHRI SATISH CHANDER Deputy Director ( P & C ), IS1 Methods of Testing Vulcanized Rubbers Subcommittee, PCDC 13:9 Conoener SHRI M. M. PATEL Mtmbws SHRI M. S. MAJU~DAR ( Alternate to Shri M. M. Pate1 ) Escon Consultants Pvt Ltd, Calcutta SARI B. CI3AKRAVARTY Andrew Yule & Co Ltd, Calcutta SHRI J. CHATTERJEE SXRI A. K. BISWAS ( Alternate ) Alkali & Chemical Corporation of India Ltd, SHRI D. K. CHATTERJEE Calcutta SRRI N. C. SANAJDAR (Alternate ) Indian Rubber Manufacturers Research AssociaSHRI K. C. DAS tion, Bombay National Test House, Calcutta SURI A. Gaosrr Cosmos India Rubber Works Pvt Ltd, Bombay SHRI C. S. INAMDAR SHRI SEN GUPTA ( Alternnte) Indian Rubber Regenerating Co Ltd, Bombay SRRI G. R. KAVISRWAR SARI P. S. VIRANI ( Alternate ) ( Continued on page 13 ) Synthetics and Chemicals Ltd, Bombay 2 IS : 3400 (Part XXI) - 1980 Indian Standard METHODS OF TEST FOR VULCANIZED PART XXI GASES DETERMINATION - CONSTANT RUBBERS TO OF PERMEABILITY PRESSURE METHOD 0. FOREWORD 0.1 This Indian Standard ( Part XXI ) was adopted by the Indian Standards Institution on 8 October 1980, after the draft finalized by the Rubber Products Sectional Committee had been approved by the Petroleum, Coal and Related Products Division Council. 0.2 The measurement of the permeability of rubber to gases is important in the evaluation of compounds for such products as inner tubes, tubeless tyre liners, hoses, balloons or other gas containers, seals and diaphragms. The measurement is also of theoretical importance in the study of characteristics of diffusion and gas solubility in relation to polymer structure. 0.3 Methods of test for vulcanized rubbers-permeability to gases by constant volume method has already been published as IS : 3400 ( Part XIX )1976. 0.4 Because of dangers connected with high pressure and flammability, handling of gases should be done by experienced personnel only. 0.5 This standard is essentially based on IS0 2782-1977 `Rubber, of permeability to gases - constant pressure vulcanized - Determination method, published by International Organization for Standardization. 0.6 In reporting the result of a test or analysis made in accordance with this standard, if the final value, observed or calculated, is to be rounded off, it shall be done in accordance with IS : 2-1960*. 1. SCOPE 1.1 This standard ( Part XXI ) prescribes the method for determination of ,permeability of vulcanized rubbers to gases at steady state condition, when a constant pressure is maintained on each of the end faces of the rubber to be tested. Results obtained by this test procedure should not be extrapolated to thickness of material considerably different from that of the test piece. *Rules for rounding off numerical values ( revised ). 3 IS : 3400 (Part 1.1.1 This 35 IRHD and petroleum gas if the gas used, XXI ) - 1980 method applies to solid rubber of a hardness not less than to gases, such as air, nitrogen, oxygen, hydrogen, liquefied (,in gaseous form ) and coal gas. Errors may be introduced appreciately swells the rubber under test. 2. TERMINOLOGY 2.0 For the purposes of this standard. the following definition shall apply. 2.1 Permeability of Rubber to Gases - The rate of volume flow of gas under steady state conditions referred to standard temperature and pressure, between opposite faces of a unit cube of solid rubber, when subjected to unit pressure difference and controlled temperature. 3. OUTLINE OF THE METHOD ( 3.1 The cavity of a test cell, maintained at a constant tempersture, is divided by a disc test piece into a high pressure and a low ( atmospheric ) pressure side. The high pressure side is connected to a constant pressure gas reservoir or is of such a volume that, once filled, it stays at a practically constant pressure. The gas permeates into the low pressure side, which is of a very low volume and connected to a capillary tube; this is provided for measuring the permeated volume, while keeping or restoring the same low pressure within this side. Absolute pressure for the high pressure side is maintained in the range of 0.3 to 1.5 MPa* and for low pressure side it is maintained at the prevailing atmospheric pressure. 3.1.1 For normal comparison of permeability of different rubber vulcanizates, the test temperature is a standard laboratory temperature ( 27 f,l"C) , but higher preferred temperature may be used where conditions are required to approximate to the service temperature of rubber products. qhen higher preferred temperatures are used, the capillary tube shall be brought to the test temperature and maintained at that temperature throughout the test. 4. APPARATUS 4.1 Test Cell 4.1.1 Test cell has means of clamping the test piece round its periphery in a gas-tight manner so as to expose one surface to gas under pressure. The other surface of the test piece shall be supported against the load due to the gas pressure so that no appreciable deformation takes place. For this reason the Iow pressure side of the test cell shall be filled with a rigid, very permeable packing piece which may consist of a disc of micro-porous material, such as microporous ebonite, discs $microporous sintered stainless steel or discs of fine wire gauze or filter paper which completely fill *I MPa=l N/mmz=approx 10 kgf/cm`J. 4 IS : 3400 ( Part XXI ) - 1980 the cavity. A means of indicating gas pressure with an error of not more than one percent shall be connected to the high pressure side of the cell. 4.1.2 The volume of the high pressure side of the cell shall be at least 25 cm3 to minimize the pressure loss due to diffusion during a test which The internal volume of the test cell on the low may last several hours. pressure ( atmospheric ) side of the test piece shall be kept to a minimum by the use of permeable packing as described above and by small diameter passages through a dismountable coupling and tubing to the capillary tube. The total free volume between test piece and zero mark shall not exceed 2 ems. Test cells shall be of metal construction with sufficient mass to assist temperature stability, and shall be provided with a drilled pocket to hold a suitable temperature measuring device. 4.2 Temperature 4.3 Volume Measuring Device -Accurate to & 02°C. Measuring Device 4.3.1 It consists fundamentally of a capillary tube of known and uniform cross section over the length used for volume measurements. Suitable cross sections are 0.7 to 2 mm2 with an accuracy of within 1 percent in uniformity. The capillary tube shall be graduated or a graduated scale It shall be suitably shall be held close to it on the long straight portion. filled with a non-volatile liquid which does not dissolve the gas [ suitable liquids are di-( 2 ethylhexyl ) sebacate or tritolyl phosphate, coloured with Sudan red 1, 4.3.2 The capillary tube may be mounted on the cell layer or may be provided with a by-pass valve in order to start the volume measurements after a conditioning period. The capillary tube may be either horizontally or vertically mounted. In the first case, only a drop of liquid may be used as index of volume variations. In the second case, a vertically adjustable reservoir of liquid connected by a T-piece to the lowest portion of the capillary tube shall be provided to restore the low side pressure. A microscope or a cathetometer may be used to observe the liquid position. 4.4 Arrangement for Maintaining Constant Temperature Constant temperature bath or other means capable of maintaining the test cell at the required test temperature to within f 1°C. The wall of the bath shall be arranged so that the outlet from the test cell will project through the side leaving the capillary dismountable coupling accessible. Examples 5. TEST of suitable apparatus are shown in Fig. 1 and 2. PIECE 5.1 Shapes and Dimensions - The test piece shall be a disc of trniform thickness and of dimensions to suit those 01 the test cell, and may be either moulded or cut from a test sheet or a product. It is preferable to use a 5 1: : 3400 ( Part XXI ) - 1980 moulded disc having on each face a circumferential rib or bead to fit into corresponding grooves in the clamping members. Where the test piece is a flat sheet, suitable `C' rings shall be used to fit into grooves in the test cell. The overall variation ( excluding beads ) in thickness shall .not exceed 10 percent of the mean thickness. 5.1.1 Suitable dimensions are 50 to 155 mm diameter with a free testing surface of 8 to 70 ems thickness may be between 0.25 and.3 mm, the smallest thickness being advantageous for rubbers of low permeability, such as isobutene-isoprene rubber. Imperfections and pinholes shall be absent. 5.2 .Number tested. of Test Pieces -Two test pieces CAPILLARY of each rubber shall be PERMEABLE 1 THERMOMETER CL FIG. 1 APPARATUS WITH HORIZONTAL MEASURING DEVICE 6. TIME LAPSE BETWEEN VULCANIZATION 6.0 Unless requirements otherwise specified for technical for time lapses shall be observed. 6 AND TESTING reasons the following IS : 3400 ( Part XXI ) - 1980 n FIG. 2 APPARATUSWITH VERTICAL MEASURING DEVICE 6.1 For all test purposes testing shall be 16 hours. the minimum time between vulcanization and 6.2 For non-product tests the maximum time between vulcanization and testing shall be 4 weeks and for evaluation intended to be comparable, the tests as far as possible, should be carried out after the same time interval. 7 IS : 3400 ( Part XXI ) - 1980 6.3 For product tests, whenever possible the time between vulcanization and testing shall not exceed 3 months. In other cases tests shall be made within 2 months of the date of receipt by the customer of the product. 7. TEMPERATURE OF TEST 7.1 For normal comparisons of permeability of different rubber vulcaniHigher temperatures may zates, the test temperature shall be 27 5 1°C. be used where conditions are required to approximate to service temperaSuch higher temperatures shall be selected from tures of rubber products. the list of preferred temperatures, namely: 40, 55, 70, 85, 100, 125, 150, 175, 200, 225 and 250°C In any given test or series of tests intended to be comparable, the tolerance on the temperature shall be & 1°C for temperatures up to 175°C and it shall be f 2°C for temperatures of 200°C and above. 8. PROCEDURE 8.1 Preparation of Test Piece 8.1.1 Examine the test piece carefully for pinholes or imperfections within the area of the internal diameter of the cell ( which is the effective Care should be taken to avoid contamination of Ihe surface test area ). Determine the thickness of the test piece between manufacture and test. in the test area as the average of six measurements each made to an Insert the permeable packing in the shallow cavity accuracy of 0.02 mm. behind the test piece on the low pressure side. Clamp the test piece securely round its periphery. NOTE It is permitted surface to secure gas-tightness. area of the test piece. to uqe a minimum of vacuu~n No grease shall be allowed grease on the clamping to appear on the central 8.1.2 Place the test cell in the constant temperature bath and connect to the test gas reservoir at the required pressure of test ( 0.3 to 1.5 MPa ) Maintain the pressure depending on the permeability of the test piece. of gas to within f 2.5 percent during the test. 8.2 Conditioning of Test Piece.2 The assembled apparatus shall be allowed to remain at the test temperature for minimum of' IG h, or \vhere the approximate va!ue of the diffusivity is known, for a minimum time t, in seconds, derived from the following equation: ha where b = thickness _ h" of the test piece in metres; 8 IS : 3400 (Part XX1 ) - 1980 Q= permeability coefficient in square metres per pasta1 second per second; and [ mV( Pa.s ) I; D = diffusion coefficient in metres squared S = solubility constant (volume of the gas dissolved per unit volume of the test piece at unit pressure) in reciprocal pascals Pa-l. This minimum time f ensures that the diffusion of gas through the test piece, and hence the gas Aow through the test piece, may reach the steady state corresponding to the right-hand (straight ) portion of the curve in Fig. 3. The left-hand portion of this curve indicates the initial approach to steady conditions due to diffusion through the test piece. The strictly linear portion of the curve only is used for permeability measurement. 0 INITIAL DlFFUSlON OF GAS TIME FIG. 3 --t TYPICAL TIME/GAS VOLUMECURVE 9 IS : 3400(Part XXI ) - 1980 of Flow Rate 8.3 Determination as described in 8.4, with 8.3.X Charge the capillary tube, calibrated Mount on the test cell and close the non-volatile liquid specified in 4.3.1. the by-pass valve, I"fany. As the gas diffuses through the test piece, the If the capillary tube is mounted vertically as in meniscus is displaced. the` apparatus shown in Fig. 2, compensate the levrls in both legs of the U-tubes by level modificationSof the reservoir as often as possible, always directly before reading. Only the levels id the U-tube are to be considered, because the level in the compensator cannot agree with the other levels due to the capillary effect of the U-tube. 8.3.2 time ). 5itart.a stop-watch when the meniscus crosses the zero mark ( zero 8.3.3 Record readings of the position of the liquid in the capillary tube at intervals of about 2 minutes throughout the test, which typically has a duration of 10 to 60 miytes after stJeady state. 8.3.4 Trace a time-length diagram; it must not show any appreciable departure from linearity after reaching a steady state. If this occurs, the test restilt shall be rejected and the test repeated. 8.4 Calibration of Capillary Tube - Introduce into the capillary tube a quantity of mercury to fill a length of about 20 mm ( Q-2 to 0.6 g ). Keeping the tube horizcntally mounted, perform the measurement of the length L of the mercury in several positions over the length of the tube ( five to ten positions ), with an accuracy of 0.02 mm. Weigh the capillary tube with aad without the mercury, to the nearegt milligram. The cross section, A1 in millimetres squared, of the capillary tube in each position in given by: where ml = mz = L P mass in mg of the. capillary mass in mg of the capillary in mmHg in g/ml of mercury. of the cross section tube w&h mercury; tube without mercdry; tube; akd = length = density in the capillary The differences between any of the measurements A, shall not exc,eed 1 percent of the mean value. "9. EXPRESSION OF RESULTS shall be calculated 9.0 The permeability in the fcllowing manner. 10 IS : 3400 ( Part XXI ) - 1980 9.1 Pressure on the low pressure side shall reading using the following relation: 1 mm of mercury be deduced Pa and the from a barometer at 0°C = 133.322 This may be corrected for thermal expansion scale, but no sea-level reduction shall be applied. of the mercury from 9.2 Pressure on the high pressure side shall be deduced meter reading ( if this is relative, PI, should be added ). the manoof 9.3 Co-ordinates of one pair of points ( or averages from many pairs) the traced time-length diagram give corresponding nt and AL values. 9.4 Permeated volume, reduced to gas reference conditions, T is: Av z &A&??% 9.5 Permeability 101 300 T ="`oo2 7 Al ALPI may be calculated b A V ", Q=&(Pz-P1)==~?l; as follows: 0*002 __-.7 b A,. ALPI I (j~z-&y) where A1 = cross section A, of the capillary tube, in sqaure metres; = free area of the test piece, in square metres; in metres; b = thickness of the test piece, AL = change in length of displacement of meniscus, in metres, obtainned on ihe linear part of the curve, during time interval of At seconds; ( absolute ) on the low pressure in metres side, in pascals; side, in pascals; second PI = pressure Pa = pressure ( absolute ) on the high pressure Q= rubber permeability, [ m2/( Pa.s )I; squared" per Pascal 7-c test temperature ( absolute ),*in kelvin; At = time interval in seconds, for a given change displacement metres, of the meniscus; in length of AL' = permeated volume of gas, at reference conditions, during the time interval of At seconds; temperature pressure ( absolute ), in kelvin; ( absolute ), Pascal. in cubic and 273 = gas reference 101 300 = gas reference For each set of two test pieces, the two values of permeability must be within 10 percent-of their mean. If they are not, determine the permeability on a further set of two test pieces and calculate the mean value of the four test results. 11 IS: 3400(Part XXI)- 1980 10.TEST REPORT 10.1The test report shall include the following particulars: a) Sample ii) details: of the sample and its origin; where appronamely, cure time and temperature, i) a full description compound details, priate; and iii) method whether b) Test details: i) the of preparation of test pieces from sample, moulded or cut and their dimensions. of test; on the high pressure and side. temperature ii) the gas used in the test; and iii) the gas pressure c) Test results: i) number d) Date of test, of test pieces tested; ii) the mean value of the permeability. 12 IS : 3400 ( Part XXI ) - 1980 ( Continwdfrom page 2 ) Mm hers ReprcJcnting Indian Petrochemical Corporation Ltd, Vadodara SHRI S. K. MAHES~WA~I DR Y. N. SRARMA ( Alternate ) Ministry of Railways DR S. P. MANIE SHRI G. DORAISWAMY ( AIternntc) National Rubber Manufacturers Ltd, Calcutta SERI R. P. MAT~UR Bayer ( India ) Ltd, Bombay SHRI R. R. PANDIT SRRI N. D. DESAI (Alternate ) Swastik Rubber Products Ltd, Pune SERI V. D. PENDSE SRRI S. V. TATHAWADXAR ( Alterno!e ) Sundarm lndustries Ltd, Madurai SERI V. R. RAO SHRI K. C. MADRUSUDEAN ( Altmate ) Bata India Ltd, Calcutta SHRX S. SARXAR SHRI s. ROY ( Alternate ) Dunlop India Ltd, Calcutta SHRI A. SHH SHRI J. C. BOSE ( Aftcrnate ) Ministry of Defence ( DGI ) SHRI B. C. SEN SHRI R. K. GUPTA ( Alternate ) Rubber Research Institute of India, Kottayam SHRI E. V. THOWAS SHRI K. 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